Wondering how store different strings in an array.
For example a user would input 'qwe' and the program would then store that in an array variable[0]. Entering another string would then store it as variable[1] and so on
int
main(int argc, char *argv[]) {
char variable[1000];
int i;
printf("enter a variable\n");
scanf("%s", variable);
for (i = 0; ??? ;i++) {
printf("The variable entered was: %s\n",variable[i]);
}
return 0;
Im new to C so I have no idea what im doing. but thats what I have came up with so far and was wondering if I could get some help with filling in the rest
Thanks!
You can use 2D array to store multiple strings. For 10 strings each of length 100
char variable[10][100];
printf("Enter Strings\n");
for (int i = 0; i < 10 ;i++)
scanf("%100s", variable[i]);
Better to use fgets to read string.
fgets(variable[i], sizeof(variable[i]), stdin);
You can also use dynamic memory allocation by using an array of pointers to char.
The most efficient way is to have an array of character pointers and allocate memory for them as needed:
char *strings[10];
int main(int ac, char *av[]) {
memset(strings, 0, 10 * sizeof(char *));
for (int i = 0; i < 10; i += 1) {
char ins[100];
scanf("%100s", ins);
strings[i] = malloc(strlen(ins) + 1);
if (strings[i]) {
strcpy(strings[i], ins);
}
}
}
variable[0] has just stored first letter of string. If you want to store multiple strings in an array you can use 2D array.
it has structure like
arr[3][100] = { "hello","world", "there"}
and you can access them as
printf("%s", arr[0]); one by one.
scanf returns number of successful readed parameters;
use 2D array for string-array
Never go out of bounds array
#include <stdio.h>
//Use defines or constants!
#define NUM_STRINGS 10
#define MAX_LENGTH_OFSTRING 1000
int main() {
char variable[NUM_STRINGS][MAX_LENGTH_OFSTRING +1 /*for '\0' Null Character */];
int i = 0;
printf("enter a variable\n");
while(scanf("%s", variable[i]) > 0){//if you print Ctrl+Z then program finish work. Do not write more than MAX_LENGTH_OFSTRING symbols
printf("The variable entered was: %s\n",variable[i]);
i++;
if(i >= NUM_STRINGS)
break;
}
return 0;
}
Related
I am trying to make an array of character Arrays. The program will read in sentences and store the sentences in a character array, and then that character array will be stored in another array. After reading numerous websites and Stack Over Flow pages I think it can be done like this. The program breaks when trying to store my character array into another array, so i'm not sure how to correct my code.
#include <stdio.h>
#include <math.h>
#include <time.h>
int main(int ac, char *av[])
{
int size; //number of sentences
char strings[100];// character array to hold the sentences
char temp;
printf("Number of Strings: ");
scanf_s("%d", &size); // read in the number of sentences to type
char **c = malloc(size); //array of character arrays
int i = 0;
int j = 0;
while (i < size) //loop for number of sentences
{
printf("Enter string %i ",(i+1));
scanf_s("%c", &temp); // temp statement to clear buffer
fgets(strings, 100, stdin);
// **** this next line breaks the program
c[i][j] = strings; // store sentence into array of character arrays
j++;
i++;
}
printf("The first character in element 0 is: %d\n", c[0][0]);
system("PAUSE");
return 0;
}
Al you need to do is allocate the memory for the string just read and copy the string:
c[i][j] = strings; // replace this with:
c[i]= malloc(strlen(strings)+1);
strcpy(c[i],strings);
Sadly char **c is not array of characters arrays. But this will properly allocate a 2d array dynamically if you follow
char (*c)[SIZE];
And then doing this
c = malloc(sizeof(char[LEN][SIZE]));
Then you do what you are trying to do.
for(size_t i = 0; i < LEN; i++){
if(fgets(c[i],SIZE,stdin)){
...
}
}
Or you can do it like this
char **c = malloc(LEN);
..
for(size_t i = 0; i < LEN; i++){
c[i] = malloc(SIZE);
...
}
But again c is nothing but jagged array of characters.
Check the return value of malloc and free the dynamically allocated memory when you are done working with it.
Listen dude,
Do you want to store the words in the character array and then store this in another array.
It is what you want ?
If yes then you can do the following.
Use stdlib by using # include <stdlib.h> .
This lets you use string functions directly.
Now read every word as a string and make array of strings.
So now if you number of strings is n, define an array for that as string my_array[n] and scan each word using scanf("%s",&my_array [i]).
In this way you will get an array of strings.
I need to write a C function that gets from the user the number of the words that he wants to enter, then the function has to scan the word from the user and but them in the array.
For example:
Program:
number of words:
User:
3
hi
my
name
(between every word there is enter) then the function has to put these words in
string array (the size of the array must be defined by malloc and the max size of the string is 100 (could be less)).
int main()
{
int n;
printf("Please enter the number of words: \n");
if (scanf("%d",&n)!=1)
return 0;
char *name;
name = malloc((sizeof(char)*100*n));
int c;
int i;
int m;
for (i = 0; i < n && ((c=getchar()) != EOF );i++)
{
name[i] = c;
}
finds_themin(&name, m); //I know this work
return 0;
}
You need to setup a pointer to pointer.
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(){
char **s;
int n;
char buffer[64];
fgets(buffer,64,stdin);
n=strtol(buffer,NULL,10);// I avoid using scanf
s=(char **)malloc(sizeof(char*)*n);// you need to declare a pointer to pointer
/*
'PtP s' would look like this:
s[0]=a char pointer so this will point to an individual string
s[1]=a char pointer so this will point to an individual string
s[2]=a char pointer so this will point to an individual string
....
so you need to allocate memory for each pointer within s.
*/
int i;
for(i=0;i<n;i++){
s[i]=(char*)malloc(sizeof(char)*100);// length of each string is 100 in this case
}
for(i=0;i<n;i++){
fgets(s[i],100,stdin);
if(strlen(s[i])>=1){// to avoid undefined behavior in case of null byte input
if(s[i][strlen(s[i])-1]=='\n'){ // fgets also puts that newline character if the string is smaller than from max length,
s[i][strlen(s[i])-1]='\0'; // just removing that newline feed from each string
}
else{
while((getchar())!='\n'); //if the string in the command line was more than 100 chars you need to remove the remaining chars for next fgets
}
}
}
for(i=0;i<n;i++){
printf("\n%s",s[i]);
}
for(i=0;i<n;i++){
free(s[i]); //avoiding leaks
}
free(s);
}
As you need to store an array of strings you need an array of char* or char** to point each string (char array).
char **name;
name = malloc(n); // to store n strings.
Then in the loop use fgets to read the input as a line. Also, you need to allocate the memory for each new char array.
fflush(stdin);
for (i = 0; i < n; i++) {
name[i] = malloc(100); // allocating memory for string.
fgets (name[i], 100, stdin); // 100 is the max len
}
You can then simply iterate over the char** array, the ith index will point to the ith string.
for (i = 0; i < n; i++) {
// printf("%s", name[i]);
}
the objective of my question is very simple. The first input that I get from the user is n (number of test cases). For each test case, the program will scan a string input from the user. And each of these strings I will process separately.
The question here is how can I get string inputs and process them separately in C language??? The idea is similar to the dictionary concept where we can have many words which are individual arrays inside one big array.
The program I have written so far:
#include <stdio.h>
#define max 100
int main (){
int n; // number of testcases
char str [100];
scanf ("%d\n",&n);
for (int i =0;i <n;i++){
scanf ("%s",&str [i]);
}
getchar ();
return 0;
}
Can someone suggest what should be done?
The input should be something like this:
Input 1:
3
Shoe
Horse
House
Input 2:
2
Flower
Bee
here 3 and 2 are the values of n, the number of test cases.
First of all, Don't be confused between "string" in C++ , and "Character Array" in C.
Since your question is based on C language, I will be answering according to that...
#include <stdio.h>
int main (){
int n; // number of testcases
char str [100][100] ; // many words , as individual arrays inside one big array
scanf ("%d\n",&n);
for (int i =0;i <n;i++){
scanf ("%s",str[i]); // since you are taking string , not character
}
// Now if you want to access i'th word you can do like
for(int i = 0 ; i < n; i++)
printf("%s\n" , str[i]);
getchar ();
return 0;
}
Now here instead of using a two-dimensional array, you can also use a one-dimensional array and separate two words by spaces, and store each word's starting position in some another array. (which is lot of implementation).
First of all yours is not C program, as you can't declare variable inside FOR loop in C, secondly have created a prototype using Pointer to Pointer, storing character array in matrix style datastructure, here is the code :-
#include <stdio.h>
#include <stdlib.h>
#define max 100
int main (){
int n,i; // number of testcases
char str [100];
char **strArray;
scanf ("%d",&n);
strArray = (char **) malloc(n);
for (i =0;i <n;i++){
(strArray)[i] = (char *) malloc(sizeof(char)*100);
scanf ("%s",(strArray)[i]);
}
for (i =0;i <n;i++){
printf("%s\n",(strArray)[i]);
free((strArray)[i]);
}
getchar ();
return 0;
}
#include <stdio.h>
#define MAX 100 // poorly named
int n=0; // number of testcases
char** strs=0;
void releaseMemory() // don't forget to release memory when done
{
int counter; // a better name
if (strs != 0)
{
for (counter=0; counter<n; counter++)
{
if (strs[counter] != 0)
free(strs[counter]);
}
free(strs);
}
}
int main ()
{
int counter; // a better name
scanf("%d\n",&n);
strs = (char**) calloc(n,sizeof(char*));
if (strs == 0)
{
printf("outer allocation failed!")
return -1;
}
for (counter=0; counter<n; counter++)
{
strs[counter] = (char*) malloc(MAX*sizeof(char));
if (strs[counter] == 0)
{
printf("allocate buffer %d failed!",counter)
releaseMemory();
return -1;
}
scanf("%s",&strs[counter]); // better hope the input is less than MAX!!
// N.B. - this doesn't limit input to one word, use validation to handle that
}
getchar();
// do whatever you need to with the data
releaseMemory();
return 0;
}
I want to store each of the 5 book names in the array and print them out. But what am I doing wrong here ?
The output prints out the last entry 5 times.
#include <stdio.h>
int main(int argc, const char * argv[])
{
char * books[5];
char currentBook[1024];
for(int i = 0; i < 5; i++)
{
printf("Enter book:\n");
gets(currentBook);
books[i] = currentBook;
}
for(int i = 0; i <5; i ++)
{
printf("Book #%d: %s\n", i, books[i]);
}
}
Given your declarations
char * books[5];
char currentBook[1024];
, this code ...
books[i] = currentBook;
... assigns books[i] to be a pointer to the beginning of array currentBook. You do that multiple times for various i, resulting in an array of pointers all pointing to the same array. When you later print the string to which each of those points, it is of course the same string.
You could approach the problem by using strdup() to make a copy of the input buffer instead of assigning each element of books to point to the same thing.
The problem is,your pointers will be pointing to the same string currentbook.
use strdup() instead to duplicate the strings:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, const char * argv[])
{
char *books[5];
char currentBook[1024];
for (int i = 0; i < 5; i++)
{
printf("Enter book:\n");
fgets(currentBook, sizeof(currentBook), stdin);
books[i] = strdup(currentBook);
}
for (int i = 0; i < 5; i++)
{
printf("Book #%d: %s\n", i, books[i]);
free(books[i]);
}
}
I want to store each of the 5 book names in the array
Then you need to define a suitable array.
Assuming you want to store 5 names, each with a maximum length of 42 characters, you need to define an array of 5 elements each being an array of 42 + 1 characters.
That is define a 2D-array of chars like this
char books [5][42 + 1]; /* Define one more char then you need to store the
`0`-terminator char ending each C "string". */
And use it like this
for(int i = 0; i < 5; i++)
{
printf("Enter book:\n");
fgets(books[i], 42 + 1, stdin);
}
On why to not use gets() you might like to read here: Why is the gets function so dangerous that it should not be used?
More on the concept of 0-terminated strings here: https://en.wikipedia.org/wiki/Null-terminated_string
If i want to take an input in a 2d array with each string in one row, and the next in the other(i.e. change the row on pressing enter). How can i do that in C. C doesnt seem to have convenient "String" Handling. I obviously mean doing so without the use of getchar().
3 ways are there which are mentioned below.
If you know the maximum number of strings and maximum number of chars, then you can use the below way to declare a 2D character array.
char strs[MAX_NO_OF_STRS][MAX_NO_CHARS] = {0};
for (i = 0; i < MAX_NO_OF_STRS; i++)
{
scanf("%s", strs[i]);
}
If you know the maximum number of strings, and you dont want to waste the memory by allocating memory for MAX_NO_CHARS for all strings. then go for array of char pointers.
char temp[MAX_NO_CHARS] = {0};
char *strs[MAX_NO_OF_STRS] = NULL;
for (i = 0; i < MAX_NO_OF_STRS; i++)
{
scanf("%s", temp);
strs[i] = strdup(temp);
}
If you know the maximum number of strings during run time means, you can declare a double pointer of char. Get the number of strings n from user and then allocate memory dynamically.
char temp[MAX_NO_CHARS] = {0};
char **strs = NULL;
int n = 0;
scanf("%d", &n);
strs = malloc(sizeof(char*) * n);
for (i = 0; i < n; i++)
{
scanf("%s", temp);
strs[i] = strdup(temp);
}
#include<stdio.h>
main()
{
char student_name[5][25];
int i;
for(i=0;i<5;i++)
{
printf("\nEnter a string %d: ",i+1);
scanf(" %[^\n]",student_name[i]);
}
}
u can read strings using 2d array without using getchar() by putting space in scanf(" %[^\n]")
; before %[^\n]!
An alternative to using malloc and filling up an array of pointers with buffers of a fixed size, would be to allocate a 2d array (in static storage or on the stack) and fill it up. KingsIndian modifed code example would than look like this:
#include <stdio.h>
int main()
{
char str[2][256] = {{0}};
int i = 0;
for(i=0;i<2;i++)
{
scanf("%255s", &str[i][0]);
}
return 0;
}
If all strings you expect to get are no longer than some size, than this approach will spare you the need to deal with freeing the memory yourself. It is less flexible however, meaning that you can't fit the size of an individual buffer to the string it contains.
EDIT
Adding to the information in the comment, to read a string that is terminated only by a new-line, rather than by any whitespace:
scanf("%255[^\n]", str[i]);